"""Network configuration via NetworkManager (nmcli)."""

import asyncio
import ipaddress
import logging
import os
import re
import shutil
from typing import Literal, Optional

from fastapi import APIRouter, Depends, HTTPException
from pydantic import BaseModel

from backend.auth import get_current_user

router = APIRouter(prefix="/api/network", tags=["network"])
log = logging.getLogger("atlus.network")

_HAS_NMCLI = bool(shutil.which("nmcli"))


# ---------------------------------------------------------------------------
# Models
# ---------------------------------------------------------------------------

class IPv4Config(BaseModel):
    method: Literal["auto", "manual"]
    address: Optional[str] = None     # CIDR notation e.g. "192.168.1.100/24"
    gateway: Optional[str] = None
    dns: Optional[list[str]] = None


class WifiConnectRequest(BaseModel):
    ssid: str
    password: Optional[str] = None
    hidden: bool = False


# ---------------------------------------------------------------------------
# Helpers
# ---------------------------------------------------------------------------

def _require_nmcli():
    """Raise 503 if NetworkManager is not available."""
    if not _HAS_NMCLI:
        raise HTTPException(503, "NetworkManager (nmcli) not available on this system")


async def _nmcli(*args: str, timeout: float = 30) -> str:
    """Run nmcli with C locale, return stdout. Raise HTTPException on failure."""
    _require_nmcli()
    cmd = ["nmcli"] + list(args)
    proc = await asyncio.create_subprocess_exec(
        *cmd,
        stdout=asyncio.subprocess.PIPE,
        stderr=asyncio.subprocess.PIPE,
        env={**os.environ, "LC_ALL": "C"},
    )
    try:
        stdout, stderr = await asyncio.wait_for(proc.communicate(), timeout=timeout)
    except asyncio.TimeoutError:
        proc.kill()
        await proc.wait()
        raise HTTPException(504, "nmcli operation timed out")

    if proc.returncode != 0:
        err_msg = stderr.decode().strip()
        log.warning("nmcli failed (%d): %s", proc.returncode, err_msg)
        raise HTTPException(500, f"nmcli error: {err_msg}")
    return stdout.decode()


def _parse_terse(output: str, fields: list[str]) -> list[dict]:
    """Parse nmcli terse (-t) colon-separated output into list of dicts.

    Handles escaped colons (\\:) in values.
    """
    results = []
    for line in output.strip().splitlines():
        if not line:
            continue
        # Split on unescaped colons
        parts = re.split(r"(?<!\\):", line)
        parts = [p.replace("\\:", ":") for p in parts]
        if len(parts) >= len(fields):
            results.append(dict(zip(fields, parts[:len(fields)])))
    return results


def _parse_keyvalue(output: str) -> dict[str, str]:
    """Parse nmcli key:value output (from `connection show <name>`)."""
    props = {}
    for line in output.strip().splitlines():
        if ":" not in line:
            continue
        key, _, value = line.partition(":")
        props[key.strip()] = value.strip()
    return props


def _validate_ipv4_config(cfg: IPv4Config):
    """Validate IPv4 configuration fields."""
    if cfg.method == "manual":
        if not cfg.address:
            raise HTTPException(422, "IP address is required for static configuration")
        if not cfg.gateway:
            raise HTTPException(422, "Gateway is required for static configuration")
        # Validate address (must be CIDR)
        try:
            ipaddress.ip_interface(cfg.address)
        except ValueError:
            raise HTTPException(422, f"Invalid IP address/prefix: {cfg.address}. Use CIDR notation (e.g. 192.168.1.100/24)")
        # Validate gateway
        try:
            ipaddress.ip_address(cfg.gateway)
        except ValueError:
            raise HTTPException(422, f"Invalid gateway address: {cfg.gateway}")
        # Validate DNS
        if cfg.dns:
            for dns in cfg.dns:
                try:
                    ipaddress.ip_address(dns)
                except ValueError:
                    raise HTTPException(422, f"Invalid DNS address: {dns}")


# ---------------------------------------------------------------------------
# Endpoints
# ---------------------------------------------------------------------------

@router.get("/status")
async def network_status(_user: str = Depends(get_current_user)):
    """Get device list and active connections."""
    _require_nmcli()

    # Device status
    dev_out = await _nmcli("-t", "-f", "DEVICE,TYPE,STATE,CONNECTION", "device", "status")
    devices = _parse_terse(dev_out, ["device", "type", "state", "connection"])

    # Filter out loopback and uninteresting devices
    devices = [d for d in devices if d["type"] in ("ethernet", "wifi", "bridge")]

    # Get IP addresses for connected devices
    for dev in devices:
        dev["ipv4"] = None
        if dev["state"] == "connected" and dev["connection"]:
            try:
                conn_out = await _nmcli("-t", "-f", "IP4.ADDRESS,IP4.GATEWAY,IP4.DNS",
                                        "connection", "show", dev["connection"])
                props = _parse_keyvalue(conn_out)
                # nmcli may output IP4.ADDRESS[1], IP4.DNS[1], etc.
                dev["ipv4"] = {
                    "address": props.get("IP4.ADDRESS[1]", ""),
                    "gateway": props.get("IP4.GATEWAY", ""),
                    "dns": [],
                }
                # Collect all DNS entries
                for k, v in props.items():
                    if k.startswith("IP4.DNS") and v:
                        dev["ipv4"]["dns"].append(v)
            except HTTPException:
                pass  # Connection details unavailable

    return {"devices": devices}


@router.get("/connections")
async def list_connections(_user: str = Depends(get_current_user)):
    """List all saved NetworkManager connections."""
    out = await _nmcli("-t", "-f", "NAME,UUID,TYPE,DEVICE", "connection", "show")
    connections = _parse_terse(out, ["name", "uuid", "type", "device"])
    return connections


@router.get("/connection/{name}")
async def connection_detail(name: str, _user: str = Depends(get_current_user)):
    """Get detailed info for a single connection."""
    try:
        out = await _nmcli("connection", "show", name)
    except HTTPException:
        raise HTTPException(404, f"Connection not found: {name}")

    props = _parse_keyvalue(out)

    # Extract IPv4 config (what's configured)
    ipv4_method = props.get("ipv4.method", "auto")
    ipv4_addresses = props.get("ipv4.addresses", "")
    ipv4_gateway = props.get("ipv4.gateway", "")
    ipv4_dns = props.get("ipv4.dns", "")

    # Extract active IPv4 (what's currently in use)
    active_address = props.get("IP4.ADDRESS[1]", "")
    active_gateway = props.get("IP4.GATEWAY", "")
    active_dns = []
    for k, v in props.items():
        if k.startswith("IP4.DNS") and v:
            active_dns.append(v)

    return {
        "name": props.get("connection.id", name),
        "uuid": props.get("connection.uuid", ""),
        "type": props.get("connection.type", ""),
        "device": props.get("GENERAL.DEVICES", props.get("connection.interface-name", "")),
        "state": props.get("GENERAL.STATE", ""),
        "ipv4": {
            "method": ipv4_method,
            "addresses": ipv4_addresses,
            "gateway": ipv4_gateway,
            "dns": ipv4_dns,
        },
        "active_ipv4": {
            "address": active_address,
            "gateway": active_gateway,
            "dns": active_dns,
        },
    }


@router.put("/connection/{name}/ipv4")
async def configure_ipv4(
    name: str,
    cfg: IPv4Config,
    _user: str = Depends(get_current_user),
):
    """Set IPv4 configuration (DHCP or static) and apply."""
    _validate_ipv4_config(cfg)

    if cfg.method == "auto":
        # Switch to DHCP — clear static settings
        await _nmcli("connection", "modify", name,
                      "ipv4.method", "auto",
                      "ipv4.addresses", "",
                      "ipv4.gateway", "",
                      "ipv4.dns", "")
    else:
        # Static configuration
        dns_str = " ".join(cfg.dns) if cfg.dns else ""
        modify_args = [
            "connection", "modify", name,
            "ipv4.method", "manual",
            "ipv4.addresses", cfg.address,
            "ipv4.gateway", cfg.gateway,
        ]
        if dns_str:
            modify_args.extend(["ipv4.dns", dns_str])
        else:
            modify_args.extend(["ipv4.dns", ""])
        await _nmcli(*modify_args)

    # Apply the changes
    try:
        await _nmcli("connection", "up", name, timeout=15)
    except HTTPException as e:
        # Connection up may fail if we just changed the IP of our own interface
        # Return success anyway — the config was saved
        log.warning("connection up after config change: %s", e.detail)

    return {"success": True, "method": cfg.method}


@router.get("/wifi/list")
async def wifi_scan(_user: str = Depends(get_current_user)):
    """Scan for available WiFi networks."""
    _require_nmcli()

    # Find the wifi device
    dev_out = await _nmcli("-t", "-f", "DEVICE,TYPE,STATE", "device", "status")
    devices = _parse_terse(dev_out, ["device", "type", "state"])
    wifi_dev = next((d for d in devices if d["type"] == "wifi"), None)
    if not wifi_dev:
        raise HTTPException(404, "No WiFi device found")

    # Scan
    try:
        out = await _nmcli("-t", "-f", "SSID,BSSID,SIGNAL,SECURITY,IN-USE",
                           "device", "wifi", "list", "--rescan", "yes",
                           timeout=20)
    except HTTPException:
        # Rescan may fail; try without rescan
        out = await _nmcli("-t", "-f", "SSID,BSSID,SIGNAL,SECURITY,IN-USE",
                           "device", "wifi", "list")

    networks = _parse_terse(out, ["ssid", "bssid", "signal", "security", "in_use"])

    # Filter empty SSIDs, deduplicate by SSID (keep strongest signal)
    seen = {}
    for net in networks:
        if not net["ssid"]:
            continue
        net["signal"] = int(net["signal"]) if net["signal"].isdigit() else 0
        net["in_use"] = net["in_use"] == "*"
        existing = seen.get(net["ssid"])
        if not existing or net["signal"] > existing["signal"]:
            seen[net["ssid"]] = net

    result = sorted(seen.values(), key=lambda x: x["signal"], reverse=True)
    return result


@router.post("/wifi/connect")
async def wifi_connect(req: WifiConnectRequest, _user: str = Depends(get_current_user)):
    """Connect to a WiFi network."""
    _require_nmcli()

    if not req.ssid or len(req.ssid) > 64:
        raise HTTPException(422, "Invalid SSID")

    args = ["device", "wifi", "connect", req.ssid]
    if req.password:
        args.extend(["password", req.password])
    if req.hidden:
        args.extend(["hidden", "yes"])

    await _nmcli(*args, timeout=30)
    return {"success": True, "ssid": req.ssid}


@router.post("/wifi/disconnect")
async def wifi_disconnect(_user: str = Depends(get_current_user)):
    """Disconnect the WiFi device."""
    _require_nmcli()

    # Find the wifi device name
    dev_out = await _nmcli("-t", "-f", "DEVICE,TYPE", "device", "status")
    devices = _parse_terse(dev_out, ["device", "type"])
    wifi_dev = next((d for d in devices if d["type"] == "wifi"), None)
    if not wifi_dev:
        raise HTTPException(404, "No WiFi device found")

    await _nmcli("device", "disconnect", wifi_dev["device"])
    return {"success": True}


@router.delete("/connection/{name}")
async def delete_connection(name: str, _user: str = Depends(get_current_user)):
    """Delete a saved connection."""
    await _nmcli("connection", "delete", name)
    return {"success": True}


@router.post("/connection/{name}/apply")
async def apply_connection(name: str, _user: str = Depends(get_current_user)):
    """Reapply/reconnect a connection."""
    await _nmcli("connection", "up", name, timeout=15)
    return {"success": True}